In order to assemble two parts together in accurate and repeatable manner, several solutions are already known that require the addition of ancillary components. For example, it is possible to use conical pins. The housings for such pins need to be made in a single operation while the two parts are accurately assembled together by specific mechanical means, thus requiring an assembly jig that is more or less complex depending on the nature of the parts to be assembled together. Once that operation has been achieved, the conical pins make it possible on each assembly operation to ensure that the two assembled-together parts return to a position that is accurately identical.
Conical holes can weaken the parts for assembling together, particularly if the parts are of small dimensions. Furthermore, conical pins can be lost during assembly and reassembly operations.
Another solution consists in indexing by means of cylindrical pegs that are engaged by force into one of the parts for assembling together, and that are received as a snug fit in corresponding bores in the other part.
The risks of weakening remain, and the machining and fitting operations remain relatively complex. Furthermore, the quality with which the two parts are positioned relative to each other depends on the fitting clearance with which the peg is engaged in the bore that receives it.
Under all circumstances, it is extremely difficult to “share” an assembly of complex shape and relatively small dimensions between a certain number of simpler parts that are positioned relative to one another, because of the numerous holes that need to be drilled.